This invention relates to compositions, processes for producing polyurethane polymers including polyurethane foams using delay action catalysts obtained when organic carboxylic acids such as organic aromatic carboxylic acids and alkyl/alkelnyl organic carboxylic di-acids are used in combination with gelling catalysts such as at least one of dimethyltin dicarboxylate salts, dimethyltin mercaptides salts and tertiary amine catalysts, and to the resultant foams.
Polyurethane foams are widely known and used in automotive, housing and other industries. Such foams are produced by reaction of a polyisocyanate with a polyol in the presence of various additives. Production of water blown foams, in which blowing is performed with CO2 generated by the reaction of water with the polyisocyanate, has therefore become increasingly important. Tertiary amine catalysts are typically used to accelerate blowing (reaction of water with polyisocyante to generate CO2) and gelling (reaction of polyol with isocyanate) reactions. The ability of the tertiary amine catalyst to selectively promote either blowing or gelling is an important consideration in selecting a catalyst for the production of particular polyurethane foam. If a catalyst promotes the blowing reaction to a high degree, much of the CO2 will be evolved before sufficient reaction of isocyanante with polyol has occurred, and the CO2 will bubble out of the formulation, resulting in a collapse of the polymerization mass yielding foam of poor quality. In contrast, if a catalyst strongly promotes the gelling reaction, a substantial portion of the CO2 will be evolved after a significant degree of polymerization has occurred. Again, poor quality foams, this time characterized by high density, excessive shrinkage, broken or poorly defined cells, or other undesirable features, will be produced. Tertiary amine catalysts generally are malodorous and offensive and many have high volatility due to their low molecular weight. Release of tertiary amine during foam processing may present significant safety and toxicity problems, and release of residual amine from customer products is generally undesirable. On the other hand, low vapor pressure-high molecular weight amine catalysts are expected to require very high catalyst usage due to their low N/C ratio making the manufacturing cost too high.
It has been generally accepted that tertiary amine catalysts containing functionalities that can chemically bind into the urethane during the reaction will limit their release from the finished product. Some representative patents of non-fugitive tertiary amine catalysts used by the industry are:
U.S. Pat. No. 4,007,140 discloses the use of N, N′-bis(3-dimethylaminopropyl)urea as a low odor catalyst for the production of polyurethanes. The patent also describes the use of N-(3-dimethylaminopropyl)-formamide as catalysts to make polyurethane foams.
Current commercially available reactive blowing catalysts structurally related to bis(dimethylamino)ethyl ether are described in U.S. Pat. Nos. 4,338,408 and 4,433,170. In particular, 2-[N-dimethylaminoethoxyethyl)-N-methylamino] ethanol is an effective blowing catalyst, albeit less effective than bis(dimethylamino)ethyl ether.
U.S. Pat. Nos. 5,508,314; 5,559,161 and 5,633,293 also states that amine catalysts containing secondary alcohols are preferred because these catalysts exhibit a desirable balance between their promotion of the active hydrogen-isocyanate reactions and their own reactivity with isocyanates. They also teach that amine catalysts containing primary alcohols react rapidly with isocyanates and therefore high use levels are required.
U.S. Pat. No. 5,859,079 describes a polyurethane catalyst composition comprising N, N′-bis(3-dimethylaminopropyl) urea and 3-dimethylaminopropylurea in a ratio that can be varied to systematically control flowability, air-flow, and force to crush.
U.S. Pat. No. 6,114,403 claims a polyurethane catalyst composition comprising N,N′-bis(3-dimethylaminopropyl) urea and 3-dimethylaminopropylurea in a ratio that can be varied to systematically control flowability, % open cell content and k-factor for rigid polyurethane foams.
U.S. Pat. No. 6,201,033 claims a reactive catalyst composition for making water blown flexible polyurethane foam. The catalyst composition comprises a tertiary amino alkyl urea and/or bis(tertiary amino alkyl) urea in combination with either a tertiary amine gelling catalyst or a tertiary amine blowing catalyst.
U.S. Pat. No. 6,232,356 claims a reactive catalyst composition for making water blown flexible polyurethane foam. The catalyst composition comprises a tertiary amino alkyl urea and/or bis(tertiary amino alkyl)urea in combination with either a gelling catalyst or a blowing catalyst. The use of such catalyst composition improves the physical properties of the polyurethane foam.
U.S. Pat. No. 6,858,654 relates to a catalyst composition for catalyzing a polyurethane foaming reaction that includes a gelling catalyst and a blowing catalyst selected such that the resulting polyurethane foam has a low level of volatile and/or malodorous material.
WO2004113410 describes a catalyst composition based on a blend of at least one tertiary amine molecule containing an isocyanate reactive group and at least one compound containing at least one quaternary ammonium alkoxide moiety and at least one tertiary amine group, wherein the later compound is partially or totally neutralized with at least one acidic compound.
U.S. Pat. Nos. 7,666,919 and 7,615,580 claims a method for making polyurethane using non-emissive catalysts in the presence of an ester alcohol or carbamate. The foams produced showed improvements to humid aged deterioration. However, the use of these additives require large use levels (1.0 pphp or higher) to have sufficient impact as to improve the physical properties according to market specifications.
Foam produced using tertiary amine catalysts containing at least one isocyanate-reactive group could overcome the issue of amine emissions but at the expense of sacrificing its chemical resistance to hydrolysis and the mechanical performance of the foam article. In addition, foam produce with non-delayed tertiary amines catalysts can generate higher level of scrap in flexible molded applications because the expanding foaming mass may not be able to properly fill the mold due to the poor flowabiltiy caused by the higher rate of viscosity increase during the polymerization process. This is also true for mold filling applications of elastomeric polyurethane polymer materials. Foam made with methane diisocyanate (MDI) using present technologies may not meet the performance requirements using conventional isocyanate-reactive tertiary amine catalysts described in the prior art. Foam made with toluene diisocyanate (TDI) completely failed to meet the minimum performance requirements using the standard procedures described above in the prior art. In the TDI case, humid aged foam have very poor mechanical properties and therefore the produced articles are not suitable for any practical use due to their expected short life. Although U.S. Pat. Nos. 7,666,919 and 7,615,580 describe a method to address this issue, the economics are unfavorable because the amount of additive needed is too high for a substantial improvement on physical properties.
The disclosure of the previously identified patents and patent applications is hereby incorporated by reference.
Therefore, there is a need in the polyurethane industry for delay action gelling catalysts that can improve the physical properties of polyurethane articles made with catalysts containing isocyanate reactive groups while improving mold filling operations in order to reduce scrap to a minimum. There is also a need to provide catalyst for elastomeric applications that can provide sufficient delay in the beginning of the polymerization process without compromising the cure of the elastomeric material.